1. Field of the Invention
This invention generally relates to a multi-speed hub for a bicycle. Such a hub can typically have a shaft, or hub axle, for being non-rotationally connected to a frame of the bicycle, a hub body rotatably mounted about the fixed shaft, and a drive element rotatably mounted on the fixed shaft. A plurality of transmission elements can preferably be disposed between the shaft and the hub body for transmitting a drive force from the drive element to the hub body. A selection between various gearing ratios provided by the transmission elements can preferably be provided by a selectively engageable ratchet mechanism and a control device for selectively engaging and disengaging the ratchet mechanisms.
More particularly, the present invention relates to such a control device for ratchet mechanisms for a multispeed drive hub of a bicycle. In general, the ratchet mechanism can preferably be formed by at least one pawl biased radially inwardly toward the stationary shaft by means of at least one spring, whereby this ratchet mechanism can, in one direction of rotation, non-rotationally couple a rang body, disposed about the axle, with another rotational body, in particular, the stationary hub axle. In addition, there can also be at least one control device running parallel to the hub axle to control the engagement of the pawl between the ring body and the hub axle.
2. Background Information
One type of control device for ratchet mechanisms, in particular for multispeed drive hubs of a bicycle, is disclosed in European Patent Application No. 0 383 350, where several ratchet mechanisms can be controlled by means of a twistable gearshift sleeve located outside the hub. On the hub described in European Patent Application No. 0 383 350, the pawls are supported on arresting teeth which are molded onto the hub axle, and the pawls are engaged and disengaged by means of apertures, control edges and bevels of the multi-part gearshift sleeve, to engage or disengage the respective connection between the pawl and the arresting teeth. If a load is to be applied to the respective pawl, this ratchet connection can only be disengaged at a point in the driving operation when the torque is low, since the bevels on the shifting sleeve cannot be made arbitrarily flat. The control device claimed by the present invention, in contrast to the known devices, lifts the pawl directly with an optimal bevel directly to a cam, whereby the angle of the bevel can be adapted to the requirements for the lifting force. It has also been determined that it would be advantageous if several cams with bevels can be located on one control plate, as this should not adversely affect the very favorable installation capabilities for the control plates.